The macrolide antibiotic erythromycin has been used successfully for a long time as a pharmaceutical preparation with bacteriostatic or bactericidal action. It is usually used in the form of esters, for example as ethyl succinate, stearate, estolate, glucoheptonate, or lactobionate, which considerably increases the volume of the finished pharmaceutical preparation because of the ester residue.
On the other hand, because the erythromycin base dissolves readily in an acid medium but only with difficulty in a basic medium, it is difficult to achieve rapid release of the active substance in the basic intestinal tract without adding large quantities of additives. By adding approximately 4-10 wt. %, based on an uncoated basic pellet, of compounds that are readily soluble in water, such as PEG, saccharose, nicotinamide, or adenosine triphosphate, rapid release of the active substance, for example in phosphate buffer with pH 7.4, could not be achieved.
On the other hand, however, the erythromycin base must be protected by an enteric coating during its passage through the stomach, because it disintegrates at a pH of &lt;4.0. Because enteric-coated preparations, for example tablets with a diameter of more than 8 mm, have been shown to remain for a long time in the stomach without disintegrating, the erythromycin base must advantageously be formulated as pellets for rapid passage through the stomach.
The aqueous preparation of erythromycin base to form pellets however entails complications because the active substance exhibits pronounced lipophilic properties and is therefore difficult to wet with water.